水科学进展

Impact of forest and grass ecosystems on the water budget of the catchments

DAI Jun-feng, CHEN Jia-zhou, CUI Yuan-lai, HE Yuan-qiu, MA Ji-gang

2006, 17(4): 435-443.

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The characteristics of the temporal-spatial distribution of the surface runoff,the percolation from the root wne,the evapotranspiration and the soil water storage of the four forest and grass ecosystems (the natural grassland,the board leaved forest land,the mixed forest land and the coniferous forest land) in the hilly region of red soil are studied with the soil and water assessment tool (SWAT) 99.2 model.The outputs of SWAT model are calibrated and validated against the observed surface runoff.Comparing the simulated monthly surface runoff with the observed one, we gain a good result with a deterministic effciency of 0.90 and an simulation efficiency of 0.74.The results shows the variation of the rainfall within a year is the rmst important factor that leads to the difference of the monthly surface runoff,the percolation and the soil water storage in the red mil area.And the annual fluctuation of weather conditions,especially the rainfall,results in the fluctuation of the water budget.Of the water outputs, the surface runoff and the percolation are influenced most by the rainfall,then the evapotranspiration.The annual fluctuation of the soil water storage is very little.Compared with the natural grassland,the forest land reduces the surface runoff more effectively,in which the board leaved forest land and the mixed forest land are preferable.The water infiltration property of the forest land is better than the natural grassland.And the evapotranspiration of the forest land is much larger than that of the natural grassland.The results show that land use mostly influences the short-term water budget in the region scale.

Hydrodynamics process of soil erosion and sediment yield by runoff on Loess Slope

LI Peng, LI Zhan-bin, ZHENG Liang-yong

2006, 17(4): 444-449.

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Based on a series of the runoff scouring experiments on slopes with their gradient ranging from 3° to 30°,the runoff energy consumption and the sediment yield is analyzed.The results show that the average flow velocity increases with the flow discharge and the slope gradient in an exponential form,and the slope gradient has greater effect on velocity than discharge.On the slope of 3°~21°,the average runoff consumption increases with slope,and decreases with slope when the slope gradient is over the critical gradient (21°~24°).The similar trends exist in the relation between the average sediment transport rate and slope.On the slope of 3°~21°,the average sediment transport rate increases with slope,and decreases with slope when the slope gradient is over the critical gradient (21°~24°).The average sediment transport rate increases with the increase of the runoff discharge,which has greater effect on the sediment yield than slope.Further the analysis indicates that there is a linear relation between the sediment transport ratio of the unit runoff width and the energy consumption of the unit runoff width.The critical energy consumption of the unit width increases with slope,while the soil erodibility decreases with the increase of slop e,whose value varies from 10.369 to 30.366,and the average value is 14.61 in the experiment across all slope.

Multiple flow direction algorithm with flow partition scheme based on downslope gradient

QIN Cheng-zhi, LI Bao-lin, ZHU A-xing, YANG Lin, PEI Tao, ZHOU Cheng-hu

2006, 17(4): 450-456.

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The estimation of flow direction is an important aspect in digital terrain analysis.There are two basic flow direction algorithms: the single flow direction algorithm (SFD) and the multiple flow direction algorithm (MFD).SFD only allows flow to follow in the steepest downslope direction and is not suited for modeling the dispersal flow over slope MFD allows flow to be distributed to all downhill neighbor cells.The currently three kinds of flow partition schemes are used by MFD algorithms: (1) weight ing the flow apportioning with constant exponent which will result in too diverging flow pattern; (2) using an accumulation based exponent which requires the accumulation distribution and an appropriate accumulation threshold determined mainly by using SFD or MFD; and (3) the "Form-based" MFD based on the analysis of the topographic form of a surface facet which is too sensitive to DEM's error.This paper presents a new MFD algorithm, MFD-fg.The basic idea of MFD-fg is that the flow partition scheme should spatially vary as the terrain changes so that the effect of the local terrain condition on the flow distribution can be reasonably modelled with the clear physical meanings.The experiments show that the linear function of the maximum downslope is an appropriate approach to measure the flow apportioning.Our experiment shows that the new approach, compared with SFD and other MFD approaches, get more reasonable flow accumulation index.

Sensitivity analysis on land data assimilation scheme of soil moisture

HUANG Chun-lin, LI Xin

2006, 17(4): 457-465.

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We develop a one-dimensional land data assimilation scheme based on the ensemble Kalman filter (EnKF) and simple biosphere model (SiB2).In order to evaluate the performance of the assimilation system, we do some assimilation experiments, using GAME-Tibet observation data from July 6 to August 9 in 1998, at the MS3608 site on the Tibetan plateau.When the current observations, in situ observations of soil moisture at the depth of 4,20 and 100 cm are assimilated into land surface model (SiB2), the best estimations of soil moisture at the surface layer, the root zone and the deep layer are calculated.We also analyze the influence of the ensemble size, the assimilation cycle, the model error, the background error and the observation error on the assimilation system.The results indicate: (1) The error in assimilation system can be reduced by increasing the ensemble members, but it will make the operation efficiency lower; (2) As for EnKF, it is unimportant for the performance of the system whether the estimation of the background is accurate; (3) The accurate estimation of the model error and the observation error can decrease the soil moisture error in the surface layer, the root zone and the deep layer; And (4) the estimation of soil moisture can be improved by using the data assimilation method.

Hydraulic characteristic parameters of macrospore flow based on spacing fractal dimension

ZHOU Ming-yao, YU Chang-hong, QIAN Xiao-qing

2006, 17(4): 466-470.

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According to the characteristic data such as the number, size and shape of the macrospore through the digital image purchase and analysis technique, the pole fractal dimensions of the two different textures are calculated and compared by using the fractal theory.The predicting model of soil moisture characteristic curve and non-saturation hydraulic conductivity are obtained by using the macrospore fractal model.The results show that the pole fractal dimension D_v can describe the soil structure of the different textures, and the model based on it produces better results compared with those of the fractal model obtained from the particle size distribution estimation.

Spatial variability of soil water infiltration in the plain of Shiyang river basin

JIA Hong-wei, KANG Shao-zhong, ZHANG Fu-cang, TONG Ling, YAO Li-min

2006, 17(4): 471-476.

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The spatial variability of the regional soil water infiltration is one of key issues now, yet there is no better ways to solve it.Based on the experiment data, the simplified Philip model of soil water infiltration and the pedo-transfer functions (PTFs) are established.By using ARCVIEW software, the distribution of infiltration parameters of the plain region of Shiyang river basin are drawed by these two models and the spatial characteristics are analyzed.The results indicate that the simplified Philip model is suitable for the study of transfer from points to region, the PTFs of the infiltration coefficient α can simply calculate the infiltration parameters, the combination of the simplified Philip model and the PTFs is the simple and beneficial method for the research of the spatial variability of the soil water infiltration characteristics of the large-scale region.

Using indicator Kriging to analyze and evaluate spatial distributions of soil water and salt in field

XU Ying, CHEN Ya-xin, WANG Jun-sheng, LIU Quan-ming

2006, 17(4): 477-482.

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The article analyzes the spatial distributions of the soil water and salt in the salinized field (55 hm²) in Huanghe Hetao irrigation area during the two critical preiod by using the multiple-variable indicator Kriging and the univariate indicator Kriging procedures,and provides the combined probability map of the soil water and salt before summer irrigation and that of soil salt at two different periods based on the chosen criteria.With the example,the article introduces in detail the principle, steps and the scope of the application of MVIK procedure.The indicator Kriging procedures are very useful to evaluate water soil resources quality at the different scales ranging from farms to regional levels and can be used as the guide for the decisionmaking and management of water-soil resources.

Application of integrated system of GIS-PModflow to water environment early warning in west of Songnen plain

TANG Jie, BIAN Jian-min, LIN Nian-feng, YANG Jian-qiang

2006, 17(4): 483-489.

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With the effect of the groundwater table changes on the environment, the coupling technology with GIS and PModflow is used to define the threshold of the groundwater environment early warning in the paper.By means of this method, the phreatic water table without salinization is defined as the maximum limit, while the pumping limit of the phreatic water as the minimum limit.On the basis of the system model generalization, the water table is simulated and predicted The spatial analysis of GIS is used for overlaying the grid and the attribute judgment.The water environment precaut ion compares the predicted water with the threshold water table.Results show that the precaution state occurs more in 2015 than 1999, and mainly with the secondary salinization due to the phreatic water table uplift.

Mitigation of landslide hazards:Case study of rainfall warning criteria

LIN Hung-chou, YU Yu-zhen, LI Guang-xin, CHEN Tien-chien

2006, 17(4): 490-495.

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Rainfall is the main factor init iating landslide hazards.Because of the improvement of weather forecast technique many studies use rainfall warning criteria to prevent landslide hazards.Unfortunately, it is hard to use in practice owing to the inaccuracy of forecast, insufficiency of hazard historical data and uncertainty of geology.This paper analyzes the relationship between landslides and characteristics of rainfall.The results show that the suitable rainfall warning criteria should be developed in accordance with different landslide hazards and pattern of rainfall.Moreover, the integrated studies combining geomechanics, engineering geology and meteorology can improve the performance of rainfall warning criteria.Consequently, the inte grated studies about mitigation of hazards are the tendency toward hazard prevention.

Plane 2D flow-water quality-sediment pollution couple model in shallow lake

GONG Chun-sheng, YAO Qi, ZHAO Di-hua, WU Yun-hai, FENG Mao-wu

2006, 17(4): 496-501.

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A water quality governing equation including sediment pollutions is derived based on the 3D advection-dispersion equation in shallow lakes.Coupled with the shallow water flow governing equations, a plane depth averaged 2D flow-water quality-sediment pollution coupled model is developed.A finite element formulation is established by using the method of Galerkin weighted residuals.A 2D real-time model for flow-water quality is developed.The simulated the dynamic hydrologic and water quality process changes with time by using the developed model.The simulated results match the measured data well, which are proved reasonable.The study provides a new approach and a practical tool for admixture flow and water quality simulation with the sediment pollutions in the shallow lake.

Effect of ecological engineering of the streams entering lake on flow velocity

TIAN Wei-jun, WANG Chao, ZHAI Jin-bo, DONG Jie

2006, 17(4): 502-506.

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The biochemical reacting area is opened up and the bionic fillers are laid directly in the stream in order to purify the stream polluted water body entering a lake and reduce the investment and energy consumption.But this will influence certainly water power condition and its existing function.In this paper, the effect of the bionic fillers on the stream power condition is analyzed by the tests.The results indicate that the turbulent effect of the 9 stems/m² bionic fillers on water flow is low and the water flow gives priority to the laminar flow because of the low velocity in the tested stream.At the same time, the in creasing rate of the roughness coefficient is low, too (the roughness coefficient of the reach with bionic fillers is only 1.08 times as much as the comparison reach), which does not influence on the drainage of the stream.

3D numerical simulation for spillway tunnel

SHA Hai-fei, WU Shi-qiang, CHEN Zhen-wen

2006, 17(4): 507-511.

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With 3D mixed element type unstructured grids, the numerical model that can simulate the 3D turbulent flow of spillway tunnel is established in this paper.The volume of fluid (VOF) method and the k-ε two-equation model for turbulent flow are adopted.The 3D Navier-Stokes equations are solved by using an improved cell-centered finite-volume method in order to eliminate the adverse influence of grid quality on stability and convergence speed.The comparison between the numerical results and the experiment data in spillway of Tankeng Hydropower Station shows a satisfactory agreement.

Experimental investigation on mixing characteristics of a round jet in co-flow

XIAO Yang, TANG Hong-wu, HUA Ming, WANG Zhi-liang

2006, 17(4): 512-517.

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In this paper, the new measuring system, including the Acoustic Doppler Velocimeter (ADV) technique, the plane laser induced fluorescence (PLIF) technique and the laboratory virtual instrument (Labview) technique, are employed to measure the quantitative time averaged and turbulent velocity fields and the scalar concentration fields of a round jet issuing into a co-flowing current.The spreading and mixing characteristics of a round jet in a co-flow are discussed and compared with the works done before.The experimental results show that the radial distributions of dimensionless mean excess velocity, concentration and turbulent intensity at the different downstream location are self similar and the distributions of velocity and concentration are overlapping to the Gaussian curve.The jet centerline velocity decays along with downstream distance increasing and follows different laws in the strong and weak jet region.

Numerical modeling of vertical 2D unsteady flow and suspended material distribution

FENG Xiao-xiang, ZHANG Xiao-feng, CUI Zhan-feng

2006, 17(4): 518-524.

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Based on the σ-coordinate transformation to fit the complicated boundary, the VOF to track the moving free surface and the SIMPLE algorithm, this paper proposes a vertical 2D unsteady flow and suspended material distribution model.It is efficiency, and able to simulate flow characteristic and transportation process of suspended material in reservoirs and rivers for the comparative uniform of the variation distribution in lateral direction.And it has an advantage over the other models with hydrostatic pressure or rigid-lid assumption.By the numerical verification of the schematic reservoir, the open-channel and trench, the model proves its reliability and validity in simulating vertical 2D flow and the concentration distribution of the suspended material.It can also give a scientific reference to flood dispatching, water pollution control and the optimization of the water diversion project, etc.

Water detection with high-resolution SAR image based on texture and imaging knowledge

ZHU Jun-jie, GUO Hua-dong, FAN Xiang-tao, DING Chi-biao, LI Li-gang, LI Yu-long

2006, 17(4): 525-530.

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In order to extract water accurately, we analyze the characteristics and the imaging mechanism of the country buildings in the synthetic aperture rader (SAR) images, and find that the water detection is interfered by the shadow of the buildings.Therefore, the water is accurately extracted from the high resolution SAR image after getting rid of the building shadows by the texture method and the knowledge-based building representation.This paper indicates that it can more accurately extract information from the high-resolution SAR images with the tradit ional methods, combining with the knowledge based methods.After extract ing water we can analyze the correlative information farther.

Numerical research on waves of a water body affecting the mean cosine of downwelling light field just beneath the surface of water

ZHAO Qiao-hua, QIN Bo-qiang

2006, 17(4): 531-537.

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The direction of incident radiance is changed by the coarse surface of waterwhich caused lry thewind.At the same tune, the reflectance, the translnittance and the geometrical structure of the incident light beneath the surface of water is also changed.In this paper, the mean cosine of the downwelling incident light fields jixst beneath different coarse surfaces due to different wind speed in a cloud free sky is investigated by means of the ray tracing.The results show that the geometrical structure of the downwelling light fields beneath the surface of water and their trends of changed are significantly affected by wind speed.When the zwnith angle of direct sunlight is small, the percentage of diffused light in the atmosphere is higher, and the decreasing mean cosine is smallwe with the incresing wind speed.While in a bigger zenith angle (as 80°), the mean cosine increase with the wind speed, and this trend is more clear with the increasing of direct sunlight.In the condition of higher percentage of the direct sunlight, the difference of the mean cosine of different zenith angle is inversed with the wind speed.This research is helpful for inversion of the inherent optical property of the water, and it can improve the precision of estimating primary production.Moreover, this method acn reduce the computations and get quite precise results.

Hydrology and storage capacity analysis of rainwater retarding practices for flood mitigation in urban area

LIAO Chao-xuan, CAI Yao-lung, HUANG Wei-min, Cheng Mow-soung

2006, 17(4): 538-542.

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This study carries on the hydrologic analysis and develops the planning procedures to determine the storage capacity of the rainwater retarding practices for the urban flood mitigation after development.The planning procedures employ the concept of the on-site control and the distributed management of small-scale rainwater retarding facilities.The computational procedure for determining rainwater retarding practices is also demonstrated by an example The conventional urban flood control method procedure is only to maintain the pre-development peak runoff by installing the detention ponds at downstream However, the procedures developed by this study can maintain both flood peak and the volume of the pre-development with less volume compared to conventional one.

Comprehensive evaluation methods for irrigation district

LI Hui-ling, WANG Xiu-gui, CUI Yuan-lai, LI Kai, FANG Bin

2006, 17(4): 543-548.

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The paper studies the methods of the fuzzy comprehensive evaluation and the grey relation analysis to evaluate the irrigation districts.To identify the indicator weight, this paper uses the game theory to harmonize and conjugate the analytical hierarchy process and the information entropy method, minimizing the deflection between the comprehensive indicator weight and the indicator weight identified with a single method.It can eliminate the unilateral result.From the evaluation, we know that this method for identifying the indicator weight is effective, furthermore, it can be operated easily, so it fits practical use.The paper takes some typical irrigation districts in Shandong province for example, the result indicates that the array orders by using the two methods are similar, so the two methods are feasible.

Available water resources in China

WANG Jian-sheng, ZHONG Hua-ping, GENG Lei-hua, XU Peng-bo, LIU Cui-shan

2006, 17(4): 549-553.

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Available water resources is the possible consumed water resources for outer rivevvay in a river basin from the point of view of water resources utilization.It has a practice significance to control the degree of water resources development and utilizatio n,study water resources rational allocation and water resources carrying capacity.Start with setting the concept of available water resources,this paper puts forward the calculation matheds for available surface water resources and total available water resources,the total available water resources in China and in the first rank areas are estimated by using the methods, and the degree,the limit and the potential of the development and utilization of water resources in China are analyzed.

Influence of Three Gorge reservoir filled with water on freshwater resource in the Yangtze River estuary

CAO Yong, CHEN Ji-yu, ZHANG Er-feng, CHENG Shen-liang, CAO Wei-cheng

2006, 17(4): 554-558.

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On June 1-15 and October 20-21,2003,the Three Chrge reserwir was filled with water.In June,the discharge at Datong hydrological station reduced by 37 percent,and the lasting time of freshwater at the observation station decreased by 40 percent.The maximum salinity and average salinity increased 3 times and 6 times,respectively.In October,the discharge at Datong station decreased by half,and the freshwater re}urce reduced,too.The maximum salinity increased 3 times compared with the averaged one.This paper discusses the aspects of the discharges along the Yangtze River,the acute change of the discharge,the time affecting the estuary and the affection factors.At last,the conclusion is drawn that the Three Chrge resemvir filled with water reduces the fresh water resource in the Yangtae River estuary.

Effect of the forest ecosystem on water quality in the water supply catchment for the middle line of South-to-North Water Transfer Project: A case study of the Huoditang forest,part of the medium altitude,southern slope of the Qinling mountain range

ZHANG Sheng-li, LI Jing, HAN Chuang-ju, WANG De-lian

2006, 17(4): 559-565.

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The objective of this research is to determine the effect of the forest ecosystem on water quality in the Huoditang Forest, part of the water supply catchment for the South-to-North Water Transfer Project.The effect of the forest on water quality was determined by measuring the water quality of rainfall and stream water collected from tributaries within the watershed and at the watershed outlet.The water flow rate in the streams was also taken into account.From July to October, rainfall was slightly acidic.The pH of the stream water was higher than that of the rainfall and was not affected by flow rate.The concentration of NO₃^-,NH₄⁺, and PO₄^3- in the stream water were lower than in the rainwater, indicating that the forest ecosystem was effective for reducing the level of these nutrients in water.This should reduce the probability of water eutrophication in the Danjiangkou Reservoir, the main water storage area for the South-to-North Project.The forest ecosystem also fixed the heavy metals Cd, Pb and Mn.This is helpful for improving water quality.The concentration of K, Na, Ca, Mg and Fe in the water increased as it passed through the region.The increases in Ca and Mg were especially large.The increases in K, Na, Ca and Mg have no effect on water quality, but the increase of Fe in the stream water improves drinking water quality.The forest ecosystem has the important function for reducing Zn in the water as it passes through the catchment area.There is no relationship between water quality and flow rate.Generally, there is no large change in water quality as flow rate varied.The results from this study show that the water quality is stabilized as it passes through the forest ecosystem.

Progress in study on the water quality purification functions of wetlands in watersheds

XI Min, LIU Hong-yu, LÜ Xian-guo

2006, 17(4): 566-573.

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Wetland,located in the terrestrial-aquatic transverse one,is an important landscape and ecosystem.It is unique combination of the structural and functional attributes that sets wetlands apart from the terrestrial and aquatic ecosystems in their ability to remove or sequester the nutrients and the toxic environmental contaminants.Wetlands have strong functions in maintaining the ecological balance and the water environment stability in watersheds.The watershced wetlands is regarded as a whole to study purification functioning.Fnrstly,this paper makes a detail introduction to purification functioning of wetlands, including their unique attributes that contribute to removal contaminant of the treatment of the wetland components and the progress in the wetland contaminant removal.Secondly,the water quality functioning of wetlands in watersheds is the importance part of this paper.In watersheds,it consists of the local and regional-scale environmental factors that have considerable influence on wetlands functioning,the wetlands functioning categorization and wetlands as a entirety to control non-point source pollution.This paper makes a summary of the watershed wetlands purification functions in particular.Finally some problems concerned are discussed and its future study is also prospected.

Advances in study on parameter identification methods for environmental models

WANG Jian-ping, CHENG Sheng-tong, JIA Hai-feng

2006, 17(4): 574-580.

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For a practical problem in the definite region, it is the most important work to identify parameter values efficiently after the structure of environmental model is defined.In fact, the model calibration is a function optimization problem, which searches the best or better parameter values in their acceptable ranges to attain a match between the observed and simulated distribution or distributions of a dependent variable or variables.By analyzing the features of parameter identification of environmental models, a survey on the identification approaches, improvements and applications and some further research contents and directions are presented.

Water-man relationship through history

ZHANG Jia-cheng

2006, 17(4): 581-584.

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The article discusses why and how the man-water relationship is dicided by the development of human society and it also strongly influences human ideology.It points out why the mathmetical modellong is not eligible for precisely predicting the disasters of flood or drought, but useful to form scientifical concept and projects adjusting man-nature system to harmoneous interaction through the methodology of engineering along with the coming of information society.

2006 Vol. 17, No. 4

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